Not really a fan of arbitrarily restricting the best feat for the verse when Macht’s ability to turn such vast quantities of land into gold has so repeatedly been associated as a staple of his power as the strongest of the Seven Sages,
Don't matter, it isn't an AP feat in the slightest. It's hax, it's treated as hax in context too.
Also at no point do they actually treat his transmutation as a symbol of actual
offensive power.
He has extremely high mana, about that of Frieren and Sol, he's powerful too, but him being the strongest due to it is more "yeah he can instantly effectively kill you and nobody can do a thing so he's unbeatable" not "he can transmute all this land which translates to him being stupidly strong".
just as Frieren’s ability to reverse such powerful magics has been much the same to hers.
Which isn't AP.
Considering the verse has an in-built mana-system as the quintessential UES the distinction seems meaningless as to why being able to transmute entire mountains into gold shouldn’t similarly scale to AP.
That isn't even how UES work. Some super weak ass magic takes mana, while some extremely strong magic is negligible, some spells have been optimized, some haven't, etc.
Frieren
doesn't even have a true "UES", let's not pretend it does, them having mana which is a universal trait, but that doesn't mean every specific spell is interchangeable in terms of mana. A mage could have a 5-B spell that costs nothing for example.
A spell within Frieren is constructed to do very specific things, flight being the obvious example where it has established constraints, benefits, and so forth, they work within these limits and rules don't stray outside of it, some spells can take less mana yet be exponentially stronger than a weaker spell that takes more mana, or a spell can do absolutely nothing in terms of offense and cost an exorbitant amount of mana, and the opposite is true too. If we legit want to calc his curse, it'd simply apply to his highly specialized curse that he spent centuries optimizing and working on without very explicit proof otherwise that it actually scales to stuff.
Honestly the verse is lucky as it is we even scale the flame tornado to general AP, because we shouldn't in the way the profiles have it framed.
I mean it's fine, but not for the reason we have it as. Frieren has the same spell, and she considers its attack output on the lower end of her kit, her lightning spell is explicitly stronger even, and characters like literally herself and Sol can deal with it just fine.